Process of treating aluminum skimmings, screenings, dross, slags, or analogous aluminous materials.



. srATEs PATENT, OFFICE.

JAMES WRIGHT LAINRIE, OF MILWAUKEE, WISCONSIN, ASSIGNOR, RY MESNE ASSIGN MENTS, TO WILLIAM F. JOBBINS, INCORPORATED,

PORATION OI JILINOIS.

OF AURORA, ILLINOIS, A COR PROCESS OI! TREATING AIJ'QMINUM SKIMMINGS, SCREENING-S, DROSS, SLAGS, OR

' ANALOGOUS A LUMINOUS MATERIALS.

I Specification of Letters Patent.

Patented Ma 29, 1917.

No Drawing. Original application filed April 8, 1913, Serial No. 759,645. Divided and this application filed September 8, 1918.

To all whom it may concern:

Be it known thatI, JAMES WRIGHT LAW- I RIE a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new U and useful Improvements in Processes of Treating Aluminum Sln'mmings, Screenmgs, Dross, Sla or Analogous Aluminous Materials, of W ich the following is a full, clear, concise, and exactdescription.

:This invention relates to a process of treating aluminum skimmings, screemngs,

dross, slags or analogousaluminous materials for thepurpose of producing therefrom certain valuable and useful products. In carrying out my invention I prefer the following procedure:

From the skimmings or analogous materials the larger amounts of free aluminum or its alloys are separated, if desired, by suitable means. This treatment leaves a residue consisting chiefly of the oxid, the carbids and the nitrids. of aluminum, and contains also the following: compounds of iron, of copper and of zinc, and free'carbon in relatively large amountsfree, finely divided aluminum and its alloys and other free metals iIL -smaller amounts; and var y proportions of soluble salts'and other 1mpurities. This residue is treated for the production of an aluminate solution by methods somewhat similar to those hitherto employed for the manufacture of this product from bauxite and otheralumina-bearin minerals or nitrids of aluminum obtaine from these minerals, but differing from these methods in order to avoid the difliculties in treatment due to the impurities found in these skimmmgs or analogous materials, which impurities are not contained in the other sources of alumina above mentioned,

, and to utilize as completely as possible those and at difl'erent times, the ciently elastic to be adaptab als obtained as will be shown herein.

substances contained as lmpurities but from which valuable products .can be obtained. Since this rawmaterial herein described varies as it is obtained from different sources rocess is suflie to all materi- The residue described may, after crushing,

if necessary, or otherwise reducing to a suitable degree of fineness, be washed with a acids or alkalis.

Serial No. 788,591.

water to 'remove the soluble salts, but if it contains a large proportion of nitridseasily decomposed by water this washing may be omitted.

The next step in the process is in the preparation of an aluminate solution by one of the two following methods: 1) by treating the materials, suitably prepared as described above, with a solution of an alkaline caustic, preferably sodium hydroxid, or (2) by fusion with an alkaline carbonate or an alkaline hydroxid and subsequently leaching the fusedmass with water.

If the former method of preparing the solution is employed, the following points.

are to be considered: It is well known that v the oxid (and possibly also the nitrids) of aluminum can exist in several modifications differing widely in case of solubility in In the materials from Which aluminate solutions are ordinarily manufactured, such as bauxite and other minerals, the aluminum is in the form of a ,diflicultly soluble aluminum oxid, probably hydrated, since all of these minerals contain a relatively large amount of water.

may be effected without the application of heat or with the application of but little heat beyond that developed by the reaction, and without the application of pressure, or with the application of but little pressure The material herein described is practically an beyond that developed as a result of the evolution-of gases (ammonia, hydrogen, hy-

drocarbons, etc.) during the course of the reaction. But, owing perhaps to a previous exposureto an unusually high temperature in the melting processes from which these materials are originally obtained, part of the oxids and of the nitride is more dilficultly ,soluble', and heating is resorted to in order to For the same reason, also, considerable variunder pressure issolve all of the available aluminous content of the material.

ation in the concentrations and the relative amounts of the caustic alkaline solution used in dissolving the aluminous content of the material is allowable and advisable. In general terms, the amounts'and concentrations should be so chosen that hydrated alumina can be precipitated without too much dilution.

The second point to be considered in the step of treating the raw,materials with a solution of alkaline caustic is that the materials contain certain compounds which, on

treatment with alkalis, give rise to a vigor ous evolution of gases consisting in part of ammonia. In this respect the materials herein described differ greatly from others heretofore used for the production of alumina, and thereforethe apparatus used forpreparing the aluminate solution must be constructed so as to allow of theescape of the gases in such a way that the ammonia.

may subsequently be separated from the other gaseous products. It is evident, as has been mentioned above, that the pressure produced by the evolution of the gases may be taken advantage of in-the, process of making the aluminate solution. The ammonia evolved may be finally absorbed in water for the production of aqueous ammonia or in1 acids for the production ofammonium sa ts.

If the secondprocess for making the alu- I minate solution is employed, the quantities of the alkali and the apparatus for the leaching must .be chosen with a view to the same considerations as those mentioned above. f.

To the aluminate solution, either before or during the process of producing it, as described, varying amounts of sulfur or of alkaline sulfid or of other sulfids are added to prevent thecontamination of the solution them if they are already present'in the soluby zinc, or copper or lead, or to remove tion. since. alkaline solutions may be thus contaminated by zinc and lead, unless the n the alkali and prevent its repeated use.

opper is caused to go into the alkaline solution apparently by thev formatio of an organic ammonia derivative, which is relatively stable but which can be decomposed and from which the copper can be precipitated in the manner described. The solutlon of copper does not always occur. It is clear that the treatmentfjust described does not only prevent the contamination of the solu--' tion by copper, zinc and lead, but it has the added advantage of leaving these substances in the residue in a form in which they are very easily extracted and converted into useful products. Furt ermore, the treatment would remove from he solution any other metals whose sulfids can be precipitated fi'om alkaline solutions. Wh11e this'is the 'used. zinc and lead are removed they rapidly use process preferred for removing the impurities above mentioned, any vother precipitation method may be employed.

After the treatment with the alkaline materials as described above has been continued until-practically all of the aluminous content (oxid, nitrids, carbids and free metal) has been dissolved, the resulting aluminate lye solution is separated from the insoluble residue by suitable means, preferably by, filtration. 7

The solid residue may now be treated for the removal of compounds of copper, of iron and of zinc by suitable means, as for mstance, by treatment with sulfuric acid, or

with other acids, whereby salts of these metals or any of their other .useful compounds may be obtained by vwell known means. As an example of the methods which may be used the following maybe cited:

The residue above described may be treated'with acids, for example, sulfuric acid, which will dissolve practically all of the copper, zinc and iron compounds. The re- 'sultin solution maybe separated from the insolu le part and the copper removed from it in several ways; for instance, the solution may be treated with zinc, thus precipitating the copper as metal and enrichlng the solu tion with zinc sulfate, or the solution may beelec'trolyized with a potential difference, such as to deposit only the copper. Both of these methods would yield copper which can be utilized as such and a solution containing zinc and iron sulfates, and both methods may be made continuous. ()r the solution above described may be treated with hydrogen sulfid in the presence of suitable amounts of acid, thus precipitating copper sulfid] which can be separated from the remaining solution. From this latter zinc sulfid may ice 1 be precipitatedby suitable regulation of the acid concentration and the variousprecipi Although theprocedure herein described is the one preferred, various changes may be made to produce the same results without departing from the spirit of the invention. Thus, for instance, if it is desired to separate the main portion of the copper from the zinc at the outset the sulfur or sulfids may be added after the aluminate lye solution has been separated from the residue containing most of the copper. Thus the zinc will be precipitated as almost pure zinc sulfid and the copper will be left behind in the residue, with other compounds from which it can be readily separated. Or, in case that very little zinc is contained in the skimmings and analogous materials as herein mentioned, which rarely occurs, the treatment with sulfur or sulfids may be omitted. Likewise the preliminary steps of the removal of the larger amounts of free metal, as well as the crushing, may not always be needed and can therefore be omitted.

Having thus described my invention, What I claim as new and desire to secure by Letters Patent is- 1. The method of utilizing aluminum skimmings, slags, dross or analogous waste aluminous materials, which consists in treating the waste materials to form an aluminate solution, separating the solution from the'solid residue and separating the copper, iron and zinc or any of them therefrom.

2. The method of utilizing aluminum skimmings, slags,. dross or analogous waste aluminous materials, which consists in treating the waste materials with a solution of v alkaline caustic, separating the resulting aluminate solution from the solid residue and separating the copper, iron and zinc or any of them therefrom. V

3. The method of utilizing aluminum skimmings, slags, dross or analogous waste aluminous materials, which consists in treating the waste materials to form an aluminate solution, precipitating as sulfids the zinc, copper and other impurities from the aluminate solution, separating the solution from thesolids and separating the copper, iron and zinc or anyof them therefrom.

4. The' method of utilizing aluminum skimmings,.slags, dross or analogous waste aluminous materials, which consistsin treating the waste materials-with a solution of alkaline caustic to produce an alumlnate soper and other impurities from the aluminate solution, separating the solution from the solids and separating the copper, iron and zinc or any of them therefrom.

. 5. The method of utilizing aluminum skimmings, slags, dross or analogous waste aluminous materials, which consists in treatalkaline caustic to produce an aluminate solution, precipitating the zinc, copper and other impurities from the aluminate solution, separating the solution from the solids,

and separatin the copper, iron and zinc or any of them t erefrom.

7. The method of utilizing aluminum skimmings, dross or analogous waste aluminous materials, which' consists in treating 'lution, precipitating as sulfids the zinc, cop-. I

the waste materials with a solution of alkaline caustic to produce an aluminate solution, precipitating the zinc, copper and other impurities ',from the aluminate solution, separating the solution from-the precipitate,

dissolving the precipitate in an acid and treating the solution with zinc to precipitate the copper therein. v

In witness whereof, I have hereunto subscribed my name in the presence of two witnesses.

Witnesses:

RICHARD A. Lommm, DONALD K. EWING.

' JAMES WRIGHT LAwRI E. 

